Nozick almost single-handedly made libertarian political philosophy respectable within mainstream academia with the 1974 publication of his now classic Anarchy, State and Utopia, which garnered a National Book Award the following year. Anarchy, State and Utopia argues, among other things, that a distribution of goods is just, so long as the distribution was brought about by free exchanges by consenting adults, even if large inequalities emerge from the process. Nozick here challenges John Rawls's arguments in A Theory of Justice that conclude that inequalities must at least make the worst off better off in order to be morally justified.

Nozick, among the leading figures in contemporary Anglo-American philosophy, made significant contributions to almost every major area of philosophy. In Philosophical Explanations, Nozick provides novel accounts of knowledge, free-will, and the nature of value. The Examined Life, pitched to a broader public, explores love, death, faith and the meaning of life. The Nature of Rationality presents a theory of practical reason that attempts to embellish notoriously spartan classical decision theory. Socratic Puzzles is a collection of papers that range from Ayn Rand and Austrian economics to animal rights, while his latest production, Invariances applies insights from physics and biology to question of objectivity in such areas as the nature of necessity and moral value.

Nozick was notable for his curious, exploratory style and methodological ecumenism. Often content to raise tantalizing philosophical possibilities and then leave judgment to the reader, Nozick was also notable for inventively drawing from literature outside of philosophy (e.g., economics, physics, evolutionary biology) to infuse his work with freshness and relevance.